Before accidentally turned into 'black' during its transportation in 17th century, tea had no 'color'.
The brew that can be called tea appeared around 2nd century in China, when sun-dried 'green' leaves were chopped and boiled as a drink, the earliest green tea. In 7th century, ancient Chinese made tea into shape of pie. Steamed, moulded, and baked dry, the pie was smashed by a roller and boiled at tea time. Pie tea was popular for a long time until banned by Emperor Hongwu in 1391.
Tea was introduced to Korea at the end of 4th century along with Buddhism. In 805 AD, a returned Japanese monk brought with him the seeds of tea from Tian-tai Mountain of Zhejiang Province and planted the first tea in Japan. (Japan has only green tea and tea-makers still use Chinese steaming method today).
Loose leaf tea, unfrequented in the past, began to be in fashion in 14th century and roasting replaced steaming method. There were 58 recorded well-known teas then. In 15 teas still in production today, 13 of them are green tea.
In 1673, England imported Chinese green tea for the first time. After franchise of tea importing being suspended by Chinese emperor, England started tea plantations in India in 1834.